I’ve always heard the Nikko blue hydrangea mentioned when speaking of the blue varieties so I thought I’d look into it. First of all, the Nikko blue will only be blue if the soil is very acidic. If you buy a Nikko blue and plant it in dirt that has a lot of lime or high alkalinity your flowers will most likely be pink. Blooms are rounded and of the mophead variety.
As with many other types of hydrangeas, this one can grow in the shade and should actually be given some shade if you live in a hot climate. I think this is the type that was planted in the front yard of my rental. It would droop on hot days as the afternoon sun beat down on the yard and I’d have to water it often in summer. They bloom in Spring / Summer and have long lasting bloom. Be careful about pruning as the new blooms grow on old wood. Don’t trim them up in Spring and remove all the new buds!
Many mail order nurseries carry this one as it’s one of the best known. I suggest checking locally for a larger size plant, since the mail order ones are small.
Honestly, this type of hydrangea has tons of info. Just google it and you’ll see.